Abstract The potential for hematopoietic stem cell therapy to cure HIV disease gains credence from the experience of the `Berlin patient' and is made more feasible by emerging developments in gene editing, particularly when coupled with non-mutating RNA based transduction strategies: the strength of Project 1. It is also now possible to credibly test anti-HIV cell therapies pre-clinically using humanized mouse models: the strength of Project 3 and Core B. What remains a challenge to reduce the complexity of hematopoietic stem cell transplant so that it may be more readily adopted in settings that are not acutely life threatening such as chronic HIV disease. Gene editing will make possible autologous cell transplant thereby removing the devastating complication of graft versus host disease. However, `conditioning' to enable stem cells to engraft the marrow is toxic and requires resource intensive hospitalization as currently practiced. We propose to use methods of modifying hematopoietic stem/progenitor cells' (HSPC) interactions with their bone marrow microenvironment to test novel, niche sparing methods to enable HSPC engraftment with reduced toxicity and potentially less cost, while assessing the impact on HIV-1 reservoirs and generation of T lymphoid reconstitution. The specific aims of this project are: Specific aim 1. Competitively advantage donor cells over endogenous stem cells through selective inhibition of eicosanoid signaling. Specific aim 2. Enhance niche vacancy without niche toxicity through manipulation of CXCR2 and heparan sulfate proteoglycan interactions between stem cells and the bone marrow niche. Specific aim 3. Selectively deplete endogenous hematopoietic cells using a novel saporin-antibody hybrid based targeting system. Specific aim 4. Test the role of conditioning in reducing the `reservoir' of HIV infected cells by comparative analysis of cytotoxic and non-cytotoxic methods of conditioning in HIV infected xenogeneic models. Test methods of enhancing T cell reconstitution to improve generation of anti-HIV-1 immunity. If successful, this project will provide specific interventions that can lower the barrier for gene edited HSPC transplantation as an approach to cure HIV/AIDS.